There are many bottle and film applications for melt processible plastics with improved barrier properties. Dispersion of platelet like fillers has the potential to improve the oxygen barrier of polymers while maintaining clarity in amorphous film; however, these materials are not suited to processes that involve orientation between the melting point and glass transition temperatures, including stretch blow molding of bottles and biaxial orientation of film, due to the formation of translucent to opaque materials It would therefore be desirable to provide improved barrier properties by use of platelet fillers while retaining the ability to form clear material upon orientation below the melting point temperature.
Many processes to form multilayer stretch blow molded bottles having 2 to 7 layers are known in the art. For example, U.S. Pat. No. 4,646,925 discloses the production of multilayer stretch blow molded bottles comprising an internal layer of unfilled polyethylene-co-vinyl alcohol.
Researchers have attempted to incorporate fillers, including platelet fillers, in an effort to improve the barrier of polyethylene-co-vinyl alcohol used in multilayer bottles; however, the bottles are opaque or have poor appearance due to the large size of the filler particles and have only a minor improvement in barrier compared to bottles prepared using unfilled polyethylene-co-vinyl alcohol due to the low aspect ratios of the filler particles. Japanese Kokai patent No. Hei 9-176461 discloses multilayer polyester bottles having an inner layer containing swellable laminar silicate. However, the laminar silicates are not well dispersed, and therefore provide little or no improvement in barrier of the resulting multilayer structure. U.S. Pat. No. 4,680,208 discloses trilayer stretch blow molded bottles comprising an internal layer of a 0.5 to 30 weight percent glass fiber reinforced composite with either polyethylene-co-vinyl alcohol, meta-xylene type polyamide, or polyethylene terephthalate. U.S. Pat. No. 4,983,432 discloses multilayer structures, including bottles, comprising a layer of a composite of polyethylene-co-vinyl alcohol and mica that has a particle size of less than about 74 microns and an aspect ratio less than 50. PCT Application WO 97/44384 is concerned with multilayer toothpaste tube bodies comprising a white, opaque layer of polyethylene-co-vinyl alcohol containing talc particles that have been delaminated by shearing to provide reduced particles size, thickness of less than 1 micron, and increased aspect ratio of less than 35. Similar efforts to delaminate mica particles have provided a reduction in particle size at the expense of a reduction in particle aspect ratio due to breakage of the mica platelets.
European Patent Applications EP 0 590 263 A2, EP 0 691 212 A1 (1996), EP 0 691 376 A1 (1996), and EP 0 761 739 A1 (1997) are concerned with water or solvent cast laminates of a composite comprised of a high hydrogen-bonding resin, such as polyvinyl alcohol and polyethylene-co-vinyl alcohol, and an inorganic laminar compound, such as sodium montmorillonite. European Patent Application EP 0 761 739 A1 (1997) further refines the above applications and is concerned with water cast films of a composite comprising either polyvinyl alcohol and polyethylene-co-vinyl alcohol and an inorganic laminar compound, such as sodium montmorillonite, that has been delaminated to provide particles with high aspect ratio by aggregating the particles by treatment of the aqueous dispersion with either acid or alumina sol prior to evaporating the solvent. However, the preparation of bottles is not contemplated, as the processes of these inventions and the films coating thereby formed are not suitable or practical for use in the manufacture of stretch blow molded bottles comprising an internal layer of the barrier substrate.
U.S. Pat. No. 5,552,469, incorporated herein by reference, describes the preparation of intercalates derived from certain phyllosilicates and water-soluble polymers such as polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene-co-vinyl alcohol, and polyacrylic acid and composite blends prepared from these intercalates. European Patent Application EP 0 846 723 A1 (1998), incorporated herein by reference, is concerned with composites comprising a matrix of polyethylene-co-vinyl alcohol and a phyllosilicate which has been intercalated with a material other than polyethylene-co-vinyl alcohol or its monomers.
There are many examples in the patent literature of polyamide/organoclay composites containing, for example, Nylon-6 and alkyl ammonium treated montmorillonite. Some patents describe the blending of up to 60 weight percent of organoclay materials with a wide range of polymers including polyamides, polyesters, polyurethanes, polycarbonates, polyolefins, vinyl polymers, thermosetting resins and the like. Such high loadings with organoclays are impractical and useless with most polymers because the melt viscosity of the blends increases so much that they cannot be molded. This is especially true with polyesters. Also, clays tend to absorb large quantities of water and attempts to blend them with preformed polyesters at elevated temperatures cause sever degradation of the molecular weight of the polyester.
The following references are of interest with regard to chemically modified organoclay materials: U.S. Pat. Nos. 4,472,538, 4,546,126, 4,676,929, 4,739,007; 4,777,206, 4,810,734; 4,889,885; 4,894,411; 5,091,462; 5,102,948, 5,153,062; 5,164,440; 5,164,460; 5,248,720; 5,382,650; 5,385,776; 5,414,042; 5,552,469; WO Pat. Application Nos. 93/04117; 93/04118; 93/11190; 94/11430, 95/06090; 95/14733; D. J. Greenland, J. Colloid Sci. 18, 647 (1963); Y. Sugahara et al., J. Ceramic Society of Japan 100, 413 (1992); P. B. Massersmith et al., J. Polymer Sci.: Polymer Chem., 33, 1047 (1995); C. O. Sriakhi et al., J. Mater. Chem. 6, 103(1996).
Among the numerous patents that describe the preparation of organoclays containing ammonium salts are U.S. Pat. Nos. 2,531,427; 2,966,506; 4,081,496, 4,105,578; 4,116,866, 4,208,218; 4,391,637; 4,410,364; 4,412,018; 4,434,075; 4,434,076, 4,450,095; 4,517,112, 4,677,158; 4,769,078; 5,110,501; and 5,334,241.
U.S. Pat. No. 4,810,734 describes a process for the preparation of a mixture of organoclay, monomer, and a dispersing medium and subsequent polymerization to obtain a polymer/organoclay composite. The dispersing medium, such as water or alcohol, is required to improve intercalation of the monomer into the organoclay and resulted in reduced process time and formation of composites with improved properties compared to the process using dry organoclay. Although polyesters are disclosed, no working example demonstrates the use of polyesters.
Example II of U.S. Pat. No. 4,889,885 describes the polycondensation of a mixture of dimethyl terephthalate, ethylene glycol, and an organoclay in water to achieve 6.2 weight percent clay in the final PET/organoclay composite. It is known that the addition of water to the preparation of Nylon-6 from caprolactam increases polymerization rate. However, addition of water and alcohols to preparations of PET will have adverse effects on reaction rate, catalyst activity, final IV, and haze in molded articles. Therefore, it is desirable to have a process that does not require the use of water or alcohol as a dispersing aid.
WO 93/04117 discloses a wide range of polymers melt blended with up to 60 weight percent of organoclay. Although use of polyesters is disclosed, specific polyester/organoclay compositions of any molecular weight are not disclosed.
WO 93/04118 discloses a composite material of a melt processible polymer and up to 60 weight percent of organoclay. Among a wide range of thermoplastic polymers, polyesters are listed as operable. Example 6 shows the melt compounding of PET and polypropylene with Claytone APA (a commercial organoclay from Southern Clay Products) in a twin screw extruder. There is no identification of the PET with regard to I.V., and the I.V. is believed to be relatively low (less than about 0.5 dl/g). There is no disclosure which would suggest how to increase the I.V. of the materials disclosed. WO 93/11190 describes similar polymer blends. All examples include polyamides as a polymer component.
U.S. Pat. No. 5,552,469 describes the preparation of intercalates derived from certain clays and water soluble polymers such as polyvinyl pyrrolidone, polyvinyl alcohol, and polyacrylic acid. Although the specification describes a wide range of thermoplastic resins including polyesters and rubbers which can be used in blends with these intercalates, there are no examples teaching how to make such blends.
U.S. Pat. No. 5,578,672 discloses the melt extrusion of a natural clay (not an organoclay), a polymer, and a liquid carrier to prepare an intercalate that is capable of exfoliating into a polymer in the melt. The preparation of intercalates with PET or its monomers with sodium montmorillonite are demonstrated; however, there are no examples teaching how to make the exfoliated composite blends.
U.S. Ser. No. 995,670 discloses a process for the preparation of clear bottles from a polyester-platelet composite by blow molding a molten parison which avoids the opacity formed during a stretch blow molding process.